netdev - Re: [PATCH net-next 05/10] net: hns3: using modulo for cyclic counters in hclge_cmd

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Message-ID: <5ef0b797-67ff-e84a-367d-bd3da96a13b3@huawei.com>
Date:   Mon, 2 Jul 2018 15:06:46 +0800
From:   "lipeng (Y)" <lipeng321@...wei.com>
To:     David Miller <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>, <yisen.zhuang@...wei.com>,
        <salil.mehta@...wei.com>
Subject: Re: [PATCH net-next 05/10] net: hns3: using modulo for cyclic
 counters in hclge_cmd_send



On 2018/6/30 20:03, David Miller wrote:
> From: Peng Li <lipeng321@...wei.com>
> Date: Fri, 29 Jun 2018 19:23:00 +0800
>
>> @@ -228,8 +228,7 @@ int hclge_cmd_send(struct hclge_hw *hw, struct hclge_desc *desc, int num)
>>   		desc_to_use = &hw->cmq.csq.desc[hw->cmq.csq.next_to_use];
>>   		*desc_to_use = desc[handle];
>>   		(hw->cmq.csq.next_to_use)++;
>> -		if (hw->cmq.csq.next_to_use == hw->cmq.csq.desc_num)
>> -			hw->cmq.csq.next_to_use = 0;
>> +		hw->cmq.csq.next_to_use %= hw->cmq.csq.desc_num;
>>   		handle++;
> I would advise against this.
>
> The "%" modulus operation takes many cpu cycles, and the current code
> is thus much faster.
>
> .
Agree with you.

Thanks for your review, we  concentrate on  the code style and ignore the
performance in this patch, It is not good.

I will remove this patch from the patchset.

>